1. Field of the Invention
This invention relates generally to magnetic sensing devices and more particularly to a magnetic sensing device for detecting vehicle speed wherein the magnetic sensing device is attached to a transmission case of an automobile.
2. Description of the Prior Art
Modern automotive parts including a magnetic sensing are required to be made lighter in view of conservation of resources and fuel. In order to meet this requirement, automobile manufacturers have utilized magnetic sensing devices having a maximum content of synthetic resins. However, in conventional speed used in detecting the rotational magnetic sensing of the output shaft of a transmission and in controlling vehicle speed, a ground is necessary for electrically detecting the rotational speed of the output shaft. Although grounding is accomplished by an electrical connection of the housing of the magnetic sensing device with the vehicle body, there is a disadvantage in that there may occur difficulty in grounding. Also a lack of mechanical strength results by reason that the housing material of the magnetic sensing device constitutes non-conductive synthetic resin. As a result, the housing of conventional magnetic sensing devices is typically made of aluminum and use of such aluminum for the housing correspondingly results in a high cost of manufacturing.